The invention generally relates to a mechanism incorporated into a handheld power tool that increases functionality or ease of usage. Principally, the invention relates to handheld ratchets driven by pneumatic, electric, hydraulic or manual power sources. More predominantly, this invention relates to a device that applies torque to a rotary fastener to tighten or loosen or otherwise adjust it by turning. In particular, the device utilizes a plurality of toothed engagements to more rapidly impart this torque.
Ratchets are generally known and used as handheld power tools in a wide variety of industries such as automotive repair and manufacturing operations. Ratchets are often energized by pneumatic motors or electric motors powered via line voltage or by way of battery. Increasing the output speed or torque of such ratchets and/or reducing the size of such ratchets will result in several benefits to society.
This invention generally relates to ratchet drive wrenches and more particularly to a powered ratchet drive wrench having a plurality of toothed members for both utilizing the full output of a drive transmission to achieve higher operating speeds of the output member and inhibiting counter-rotation of the output member.
The invention is especially concerned with a powered wrench that rotates an output member with an attached socket for turning a fastener element such as a bolt or a nut. Wrenches of this type are useful in automotive repair and industrial applications. Conventionally, pneumatic or air ratchet drive wrenches comprise an air motor for powering the wrench, an internal ratchet mechanism for transferring motion of the motor and an output member for transmitting such motion to a work piece. Put simply, the internal ratchet mechanism typically includes a rotating offset shaft spinning proportionately with the air motor that in turn pivots a rocker having pawls attached which repeatedly engage sets of teeth on intermediate toothed members which subsequently engage the output member, causing the member to rotate in a desired direction. During each rotation of the air motor, the output member is rotated a fraction of a revolution. By repeatedly engaging the output member and rotating it only a short distance, great mechanical advantage is obtained and the high-speed rotation of the air motor is readily converted to a high-torque, yet more slowly rotating, output member. Instead of a pneumatic motor an electric motor powered by line voltage through a cord or a cordless motor powered by batteries or any other type of motor may be used to drive the ratchet mechanism. These advantages are well understood in the relevant art.
Despite the simplicity of the concept behind a powered ratchet drive wrench, the internal ratchet mechanisms of conventional powered ratchet drive wrenches are complex and require many parts interacting with one another. For instance, wrenches traditionally require complex mechanisms for ensuring that the output member of the wrench does not rotate counter the desired direction during wrench use. These mechanisms often include multiple parts that serve the limited purpose of inhibiting counter-rotation of the output member. Similarly, size and space limitations of the wrench often compel the fashioning of elaborate, interactive components. Simplification of such a wrench by eliminating redundant parts and reducing the size and complexity of required parts improves overall wrench design.
Current ratchet wrench designs utilize only half the output of the transmission drive between the ratchet mechanism and the driving force, whether that be from a motor or by hand action. The output member incrementally rotates a few degrees, performing the desired work, during the power stroke half of the transmission drive output. During the other half of the output of the transmission drive the mechanism is “ratcheting” where the output member is stationary and the driving pawl slips out of engagement during a retracting motion. In the case of a motor-driven ratchet mechanism the transmission driving the ratchet mechanism still has power available to drive the output member against its resistance of the fastener, but it is effectively disengaged due to the retracting motion of the pawls and the subsequent disengaging ratchet action. Utilization of this wasted power improves the overall wrench effectiveness by increasing the amount of work accomplished.
It is an aim of wrench manufacturers to provide a power driven wrench that uses energy efficiently. One difficulty in the fashioning of such a wrench is providing an output member that may rotate in both directions, yet will not rotate opposite the desired direction during the requisite ratcheting retraction stroke between subsequent pawl engagements.
Non-continuous drive ratchets need a means to prevent counter-rotation and they all employ special parts solely for this purpose. Most, if not all, of these counter-rotation devices employ a method to create a frictional drag sufficient enough to prevent counter-rotation. However, this drag is a frictional force that resists motion and is always present, even when counter-rotation is not needed and the pawl is driving the output member. Thus, some of the tool's output is diminished by having to overcome this parasitic friction. Typically, those wrenches include frictional pressure washers for impeding counter-rotation of the output member, while other configurations incorporate stop mechanisms of increased complexity and cost. The invention at hand does not incorporate any components whose sole purpose is to provide the counter-rotation function. The design inherently achieves the counter-rotation necessary by continuously driving the output member.
The invention at hand manages energy more efficiently by utilizing the otherwise wasted retraction-only motion of the transmission drive, thus doubling the effective of the output drive member.